I have a Simulink model with 6 parameters of 6 gain blocks. I specified them as the Simulink parameters directly for each gain block in the model. I also specified 6 initial values for these parameters. Then, I used the parameter estimation function in the Simulink design optimization tool to estimate the 6 gain parameters following my input/output experiment data. But I could not select these parameters to estimate (the boxes next to the parameters could not be checked as in the attachment). I would appreciate if someone could advise me on this.